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<CENTER><H1 ALIGN="CENTER">How to use the STL documentation</H1>
</CENTER><P>
This site documents all of the components (classes, functions, and 
concepts) in the SGI Standard Template Library. Each page describes a 
single component, and also includes links to related components. </P>
<P>
This documentation assumes a general familiarity with C++, especially 
with C++ templates. Additionally, you should read <A
 HREF="stl_introduction.html">Introduction to the Standard Template 
Library</A> before proceeding to the pages that describe individual 
components: the introductory page defines several terms that are used 
throughout the documentation.</P>
<H2>
Classification of STL components</H2>
<P>
The STL components are divided into six broad categories on the basis 
of functionality: <I>Containers</I>, <I>Iterators</I>, <I>Algorithms</I>, <I>Function 
Objects</I>, <I>Utilities</I>, and <I>Allocators</I>; these categories 
are defined in the <A HREF="stl_introduction.html">Introduction</A>, 
and the <A HREF="table_of_contents.html">Table of Contents</A> is 
organized according to them. </P>
<P>
The STL documentation contains two indices. One of them, the <A
 HREF="stl_index.html">Main Index</A>, lists all components in 
alphabetical order. The other, the <A HREF="stl_index_cat.html">Divided 
Index</A>, contains a separate alphabetical listing for each category. 
The Divided Index includes one category that is not present in the 
Table of Contents: <I>Adaptors</I>. An adaptor is a class or a 
function that transforms one interface into a different one. The reason 
that adaptors don't appear in the Table of Contents is that no 
component is merely an adaptor, but always an adaptor and something 
else; <TT><A href="stack.html">stack</A></TT>, for example, is a container and an adaptor. 
Accordingly, <TT><A href="stack.html">stack</A></TT> appears in two different places in the 
Divided Index. There are several other components that appear in the 
Divided Index in more than one place. </P>
<P>
The STL documentation classifies components in two ways.
<OL>
    <LI><i>Categories</i> are a classification by functionality.
        The categories are:
        <UL>
            <LI>Container
            <LI>Iterator
            <LI>Algorithm
            <LI>Function Object
            <LI>Utility
            <LI>Adaptor
            <LI>Allocator.
        </UL>
    <LI><i>Component types</i> are a structural classification: one
        based on what kind of C++ entity (if any) a component is.  The
        component types are:
        <UL>
            <LI>Type (<i>i.e.</i> a <TT>struct</TT> or <TT>class</TT>)
            <LI>Function
            <LI>Concept (as defined in the 
                <A HREF="stl_introduction.html">Introduction</A>).
        </UL>
</OL>
</P>
<P>
These two classification schemes are independent, and each of them 
applies to every STL component; <TT><A href="Vector.html">vector</A></TT>, for example, is a <I>type</I>
 whose category is <I>Containers</I>, and <B><A href="ForwardIterator.html">Forward Iterator</A></B>
 is a <I>concept</I> whose category is <I>Iterators</I>. </P>
<P>
Both of these classification schemes appear at the top of every page 
that documents an STL component. The upper left corner identifies the 
the component's category as <I>Containers</I>,<I> Iterators</I>, <I>Algorithms</I>, <I>Function 
Objects</I>, <I>Utilities</I>, <I>Adaptors</I>, or <I>Allocators</I>, 
and the upper right corner identifies the component as a <I>type</I>, a <I>function</I>, 
or a <I>concept</I>. </P>
<H2>
Using the STL documentation</H2>
<P>
The STL is a <I>generic</I> library: almost every class and function is 
a template. Accordingly, one of the most important purposes of the STL 
documentation is to provide a clear description of which types may be 
used to instantiate those templates. As described in the <A
 HREF="stl_introduction.html">Introduction</A>, a <I>concept </I>is a 
generic set of requirements that a type must satisfy: a type is said to 
be a <I>model of</I> a concept if it satisfies all of that concept's 
requirements. </P>
<P>
Concepts are used very heavily in the STL documentation, both because 
they directly express type requirements, and because they are a tool 
for organizing types conceptually. (For example, the fact that <TT><A href="ostream_iterator.html">ostream_iterator</A></TT>
and <TT><A href="insert_iterator.html">insert_iterator</A></TT> are both models of <B><A href="OutputIterator.html">Output Iterator</A></B> 
is an important statement about what those two classes 
have in common.) Concepts are used for the documentation of both <I>types</I>
 and <I>functions</I>.</P>
<H3>
The format of a <I>concept </I>page</H3>
<P>
A page that documents a <I>concept</I> has the following sections. </P>
<UL>
    <LI>
    <B>Summary:</B> A description of the concept's purpose.
    <LI>
    <B>Refinement of:</B> A list of other concepts that this concept <I>refines</I>, 
    with links to those concepts. 
    <LI>
    <B>Associated types:</B> A concept is a set of requirements on some 
    type. Frequently, however, some of those requirements involve some 
    other type. For example, one of the<B> <A href="UnaryFunction.html">Unary Function</A></B>
     requirements is that a <B><A href="UnaryFunction.html">Unary Function</A></B> must have an <I>argument 
    type</I>; if <TT>F</TT> is a type that models <B><A href="UnaryFunction.html">Unary Function</A></B>
     and <TT>f</TT> is an object of type <TT>F</TT>, then, in the 
    expression <TT>f(x)</TT>, <TT>x</TT> must be of <TT>F</TT>'s 
    argument type. If a concept does have any such associated types, then 
    they are defined in this section.
    <LI>
    <B>Notation</B>: The next three sections, <B>definitions</B>, <B>valid 
    expressions</B>, and <B>expression semantics</B>, present 
    expressions involving types that model the concept being defined. This 
    section defines the meaning of the variables and identifiers used in 
    those expressions.
    <LI>
    <B>Definitions</B>: Some concepts, such as <B><A href="LessThanComparable.html">LessThan Comparable</A></B>, 
    use specialized terminology. If a concept requires 
    any such terminology, it is defined in this section.
    <LI>
    <B>Valid Expressions</B>: A type that models a concept is required 
    to support certain operations. In most cases, it doesn't make sense to 
    describe this in terms of specific functions or member functions: it 
    doesn't make any difference, for example, whether a type that models 
    <B><A href="InputIterator.html">Input Iterator</A></B> uses a global function or a member function to 
    provide <TT>operator++</TT>. This section lists the expressions 
    that a type modeling this concept must support. It includes any 
    special requirements (if any) on the types of the expression's 
    operands, and the expression's return type (if any). 
    <LI>
    <B>Expression Semantics:</B> The previous section, <B>valid 
    expressions</B>, lists which expressions involving a type must be 
    supported; it doesn't, however, define the meaning of those 
    expressions. This section does: it lists the semantics, preconditions, 
    and postconditions for the expressions defined in the previous section. 
    <LI>
    <B>Complexity Guarantees</B>: In some cases, the run-time 
    complexity of certain operations is an important part of a concept's 
    requirements. For example, one of the most significant distinctions 
    between a <B><A href="BidirectionalIterator.html">Bidirectional Iterator</A></B> and a 
    <B><A href="RandomAccessIterator.html">Random Access Iterator</A></B> is that, for random access iterators, 
    expressions like <TT>p + n</TT> take constant time. Any such 
    requirements on run-time complexity are listed in this section.
    <LI>
    <B>Invariants:</B> Many concepts require that some property is 
    always true for objects of a type that models the concept being 
    defined. For example, <B><A href="LessThanComparable.html">LessThan Comparable</A></B> imposes the 
    requirement of <I>transitivity</I>: if <TT>x &lt; y</TT> and <TT>y 
    &lt; z</TT>, then <TT>x &lt; z</TT>. Some such properties are 
    &quot;axioms&quot; (that is, they are independent of any other 
    requirements) and some are &quot;theorems&quot; (that is, they follow 
    either from requirements in the <B>expression semantics</B> section 
    or from other requirements in the <B>invariants</B> section). 
    <LI>
    <B>Models</B>: A list of examples of types that are models of this 
    concept. Note that this list is not intended to be complete: in most 
    cases a complete list would be impossible, because there are an 
    infinite number of types that could model the concept.
    <LI>
    <B>Notes</B>: Footnotes (if any) that are referred to by other 
    parts of the page. 
    <LI>
    <B>See Also</B>: Links to other related pages.
</UL>
<H3>
The format of a <I>type </I>page</H3>
<P>
A page that documents a <I>type</I> has the following sections. </P>
<UL>
    <LI>
    <B>Description</B>. A summary of the type's properties.
    <LI>
    <B>Example of use</B>: A code fragment involving the type.
    <LI>
    <B>Definition</B>: A link to the source code where the type is 
    defined. 
    <LI>
    <B>Template parameters</B>: Almost all STL structs and classes are 
    templates. This section lists the name of each template parameter, its 
    purpose, and its default value (if any).
    <LI>
    <B>Model of</B>: A list of the concepts that this type is a model 
    of, and links to those concepts. Note that a type may be a model of 
    more than one concept: <TT><A href="Vector.html">vector</A></TT>, for example, is a model 
    of both <B><A href="RandomAccessContainer.html">Random Access Container</A></B> and 
    <B><A href="BackInsertionSequence.html">Back Insertion Sequence</A></B>. If a type is a model of two different concepts, that 
    simply means that it satisfies the requirements of both.
    <LI>
    <B>Type requirements</B>: The template parameters of a class 
    template usually must satisfy a set of requirements. Many of these can 
    simply be expressed by listing which concept a template parameter must 
    conform to, but some type requirements are slightly more complicated, 
    and involve a relationship between two different template parameters. 
    <LI>
    <B>Public base classes</B>: If this class inherits from any other 
    classes, they are listed in this section.
    <LI>
    <B>Members</B>: A list of this type's nested types, member 
    functions, member variables, and associated non-member functions. In 
    most cases these members are simply listed, rather than defined: since 
    the type is a model of some concept, detailed definitions aren't 
    usually necessary. For example, <TT><A href="Vector.html">vector</A></TT> is a model of <B><A href="Container.html">Container</A></B>, 
    so the description of the member function <TT>begin()</TT> in the <B><A href="Container.html">Container</A></B>
     page applies to <TT><A href="Vector.html">vector</A></TT>, and there is no need to 
    repeat it in the <TT><A href="Vector.html">vector</A></TT> page. Instead, the <B>Members</B>
     section provides a very brief description of each member and a link to 
    whatever page defines that member more fully.
    <LI>
    <B>New Members:</B> A type might have some members that are not 
    part of the requirements of any of the concepts that it models. For 
    example, <A href="Vector.html">vector</A> has a member function called <TT>capacity()</TT>, 
    which is not part of the <B><A href="RandomAccessContainer.html">Random Access Container</A></B> or 
    <B><A href="BackInsertionSequence.html">Back Insertion Sequence</A></B> requirements. These members are defined in 
    the <B>New members</B> section.
    <LI>
    <B>Notes</B>: Footnotes (if any) that are referred to by other 
    parts of the page. 
    <LI>
    <B>See Also</B>: Links to other related pages.
</UL>
<H3>
The format of a <I>function </I>page</H3>
<P>
A page that documents a <I>function</I> has the following sections. </P>
<UL>
    <LI>
    <B>Prototype:</B> the function's declaration. 
    <LI>
    <B>Description:</B> A summary of what the function does.
    <LI>
    <B>Definition</B>: A link to the source code where the function is 
    defined. 
    <LI>
    <B>Requirements on types:</B> Most functions in the STL are function 
    templates. This section lists the requirements that must be satisfied 
    by the function's template parameters. Sometimes the requirements can 
    simply be expressed by listing which concept a template parameter must 
    conform to, but sometimes they are more complicated and involve a 
    relationship between two different template parameters. In the case of <TT><A href="find.html">find</A></TT>, 
    for example, the requirements are that the  parameter <TT>InputIterator</TT>
     is a model of <B><A href="InputIterator.html">Input Iterator</A></B>, that the parameter <TT>EqualityComparable</TT>
     is a model of <B><A href="EqualityComparable.html">Equality Comparable</A></B>, and that comparison 
    for equality is possible between objects of type <TT>EqualityComparable</TT>
     and objects of <TT>InputIterator</TT>'s value types. 
    <LI>
    <B>Preconditions:</B> Functions usually aren't guaranteed to yield 
    a well-defined result for any possible input, but only for valid input; 
    it is an error to call a function with invalid input. This section 
    describes the conditions for validity. 
    <LI>
    <B>Complexity:</B> Guarantees on the function's run-time 
    complexity. For example, <TT><A href="find.html">find</A></TT>'s run-time complexity is 
    linear in the length of the input range. 
    <LI>
    <B>Example of use:</B> A code fragment that illustrates how to use 
    the function.
    <LI>
    <B>Notes</B>: Footnotes (if any) that are referred to by other 
    parts of the page. 
    <LI>
    <B>See Also</B>: Links to other related pages.
</UL>

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